1. Field of the Invention
One or more embodiments of the present invention relates to a battery pack monitoring apparatus that detects, in a battery pack which is constituted of a plurality of battery cells connected in series, line breakage of detection lines connected to both electrodes of each of the battery cells in order to detect a voltage of each of the battery cells.
2. Background Art
For example, as shown in Japanese Unexamined Patent Publication Nos. 2005-168118, 2009-257923, and 2010-11722, a battery pack is constituted of a plurality of battery cells connected in series. Detection lines are connected to positive and negative electrodes of each of the battery cells. These detection lines are connected to respective abnormality detectors of a battery pack monitoring apparatus (an abnormality detection apparatus for battery pack) through respective connectors. The abnormality detectors detect voltages of the battery cells through the detection lines, and determine charge/discharge abnormality in the battery cells based on the detected voltage values.
In Japanese Unexamined Patent Publication No. 2005-168118, transistors provided corresponding to respective battery cells are forced to be alternately turned on and off by outputting line breakage diagnosis conducting signals and an overcharge/overdischarge detection switching signal from an overcharge/overdischarge control circuit. Further, transistors to be turned on and transistors to be turned off are switched so as to be alternately turned on and off. Then, line breakage of a detection line connected between adjacent battery cells is detected based on a level of a signal (H or L) output from an abnormality detection circuit.
In Japanese Unexamined Patent Publication No. 2009-257923, zener diodes each having a reaction voltage equal to or higher than an overcharge determination voltage as well as equal to or lower than twice the overcharge determination voltage are connected to respective battery cells in parallel. Further, line breakage of a detection line connected between adjacent battery cells is detected based on detection states of overcharge abnormality and overdischarge abnormality of the adjacent battery cells.
In Japanese Unexamined Patent Publication No. 2010-11722, a polarity inversion detecting circuit is connected to first, second, and third detection lines from a highest potential side of a battery pack. Further, another polarity inversion detecting circuits is connected to first, second, and third detection lines from a lowest potential side of the battery pack. Further, line breakage of each of the first detection line from the highest potential side and the first detection line from the lowest potential side is detected based on a level of a signal (H or L) output from each of the polarity inversion detecting circuits according to each of voltage polarity inversion states between the first detection line from the highest potential side and a detection line adjacent thereto and between the first detection line from the lowest potential side and a detection line adjacent thereto. Further, diodes are connected to the respective battery cells in parallel in order to protect components inside the apparatus from electrostatic generated in connectors.
As described above, in the apparatuses of Japanese Unexamined Patent Publication Nos. 2005-168118 and 2009-257923, although line breakage of a detection line that is connected between adjacent battery cells is detected, it is not possible to detect line breakage of a highest potential side detection line and a lowest potential side detection line which are connected to respective ends of the battery pack. In the apparatus of Japanese Unexamined Patent Publication No. 2010-11722, because line breakage of each of the highest potential side detection line and the lowest potential side detection line is detected based on a level of a signal output from each of the polarity inversion detecting circuits, it is necessary to provide the polarity inversion detecting circuit at each of the highest potential side and the lowest potential side.